[Docs] Add gtk-doc comments to hb-ft.

src/hb-ft.cc

@@ -46,8 +46,13 @@
  * @short_description: FreeType integration
  * @include: hb-ft.h
  *
- * Functions for using HarfBuzz with the FreeType library to provide face and
+ * Functions for using HarfBuzz with the FreeType library.
+ *
+ * HarfBuzz supports using FreeType to provide face and
  * font data.
+ *
+ * <note>Note that FreeType is not thread-safe, therefore these
+ * functions are not thread-safe either.</note>
  **/
 
 
@@ -125,10 +130,13 @@ _hb_ft_font_destroy (void *data)
 
 /**
  * hb_ft_font_set_load_flags:
- * @font:
+ * @font: #hb_font_t to work upon
- * @load_flags:
+ * @load_flags: The FreeType load flags to set
  *
+ * Sets the FT_Load_Glyph load flags for the specified #hb_font_t.
  *
+ * For more information, see 
+ * https://www.freetype.org/freetype2/docs/reference/ft2-base_interface.html#ft_load_xxx
  *
  * Since: 1.0.5
  **/
@@ -148,11 +156,15 @@ hb_ft_font_set_load_flags (hb_font_t *font, int load_flags)
 
 /**
  * hb_ft_font_get_load_flags:
- * @font:
+ * @font: #hb_font_t to work upon
  *
+ * Fetches the FT_Load_Glyph load flags of the specified #hb_font_t.
  *
+ * For more information, see 
+ * https://www.freetype.org/freetype2/docs/reference/ft2-base_interface.html#ft_load_xxx
+ *
+ * Return value: FT_Load_Glyph flags found
  *
- * Return value:
  * Since: 1.0.5
  **/
 int
@@ -166,6 +178,17 @@ hb_ft_font_get_load_flags (hb_font_t *font)
   return ft_font->load_flags;
 }
 
+/**
+ * hb_ft_get_face:
+ * @font: #hb_font_t to work upon
+ *
+ * Fetches the FT_Face associated with the specified #hb_font_t
+ * font object.
+ *
+ * Return value: the FT_Face found
+ *
+ * Since: 1.0.5
+ **/
 FT_Face
 hb_ft_font_get_face (hb_font_t *font)
 {
@@ -570,12 +593,22 @@ reference_table  (hb_face_t *face HB_UNUSED, hb_tag_t tag, void *user_data)
 
 /**
  * hb_ft_face_create:
- * @ft_face: (destroy destroy) (scope notified):
+ * @ft_face: (destroy destroy) (scope notified): FT_Face to work upon
- * @destroy:
+ * @destroy: A callback to call when the face object is not needed anymore
  *
+ * Creates an #hb_face_t face object from the specified FT_Face.
  *
+ * This variant of the function does not provide any life-cycle management.
+ *
+ * Most client programs should use hb_ft_face_create_referenced()
+ * (or, perhaps, hb_ft_face_create_cached()) instead. 
+ *
+ * If you know you have valid reasons not to use hb_ft_face_create_referenced(),
+ * then it is the client program's responsibility to destroy @ft_face 
+ * after the #hb_face_t face object has been destroyed.
+ *
+ * Return value: (transfer full): the new #hb_face_t face object
  *
- * Return value: (transfer full):
  * Since: 0.9.2
  **/
 hb_face_t *
@@ -605,11 +638,19 @@ hb_ft_face_create (FT_Face           ft_face,
 
 /**
  * hb_ft_face_create_referenced:
- * @ft_face:
+ * @ft_face: FT_Face to work upon
  *
+ * Creates an #hb_face_t face object from the specified FT_Face.
  *
+ * This is the preferred variant of the hb_ft_face_create*
+ * function family, because it calls FT_Reference_Face() on @ft_face,
+ * ensuring that @ft_face remains alive as long as the resulting
+ * #hb_face_t face object remains alive.
+ *
+ * Use this version unless you know you have good reasons not to.
+ *
+ * Return value: (transfer full): the new #hb_face_t face object
  *
- * Return value: (transfer full):
  * Since: 0.9.38
  **/
 hb_face_t *
@@ -627,11 +668,21 @@ hb_ft_face_finalize (FT_Face ft_face)
 
 /**
  * hb_ft_face_create_cached:
- * @ft_face:
+ * @ft_face: FT_Face to work upon
  *
+ * Creates an #hb_face_t face object from the specified FT_Face.
  *
+ * This variant of the function caches the newly created #hb_face_t
+ * face object, using the generic pointer of @ft_face. Subsequent function
+ * calls that are passed the same @ft_face parameter will have the same
+ * #hb_face_t returned to them, and that #hb_face_t will be correctly
+ * reference counted.
+ *
+ * However, client programs are still responsible for destroying
+ * @ft_face after the last #hb_face_t face object has been destroyed.
+ *
+ * Return value: (transfer full): the new #hb_face_t face object
  *
- * Return value: (transfer full):
  * Since: 0.9.2
  **/
 hb_face_t *
@@ -649,15 +700,28 @@ hb_ft_face_create_cached (FT_Face ft_face)
   return hb_face_reference ((hb_face_t *) ft_face->generic.data);
 }
 
-
 /**
  * hb_ft_font_create:
- * @ft_face: (destroy destroy) (scope notified):
+ * @ft_face: (destroy destroy) (scope notified): FT_Face to work upon
- * @destroy:
+ * @destroy: (optional): A callback to call when the font object is not needed anymore
  *
+ * Creates an #hb_font_t font object from the specified FT_Face.
  *
+ * <note>Note: You must set the face size on @ft_face before calling
+ * hb_ft_font_create() on it. Otherwise, HarfBuzz will not pick up
+ * the face size.</note>
+ *
+ * This variant of the function does not provide any life-cycle management.
+ *
+ * Most client programs should use hb_ft_font_create_referenced()
+ * instead. 
+ *
+ * If you know you have valid reasons not to use hb_ft_font_create_referenced(),
+ * then it is the client program's responsibility to destroy @ft_face 
+ * after the #hb_font_t font object has been destroyed.
+ *
+ * Return value: (transfer full): the new #hb_font_t font object
  *
- * Return value: (transfer full):
  * Since: 0.9.2
  **/
 hb_font_t *
@@ -675,6 +739,16 @@ hb_ft_font_create (FT_Face           ft_face,
   return font;
 }
 
+/**
+ * hb_ft_font_has_changed:
+ * @font: #hb_font_t to work upon
+ *
+ * Refreshes the state of @font when the underlying FT_Face has changed.
+ * This function should be called after changing the size or
+ * variation-axis settings on the FT_Face.
+ *
+ * Since: 1.0.5
+ **/
 void
 hb_ft_font_changed (hb_font_t *font)
 {
@@ -730,11 +804,23 @@ hb_ft_font_changed (hb_font_t *font)
 
 /**
  * hb_ft_font_create_referenced:
- * @ft_face:
+ * @ft_face: FT_Face to work upon
  *
+ * Creates an #hb_font_t font object from the specified FT_Face.
  *
+ * <note>Note: You must set the face size on @ft_face before calling
+ * hb_ft_font_create_references() on it. Otherwise, HarfBuzz will not pick up
+ * the face size.</note>
+ *
+ * This is the preferred variant of the hb_ft_font_create*
+ * function family, because it calls FT_Reference_Face() on @ft_face,
+ * ensuring that @ft_face remains alive as long as the resulting
+ * #hb_font_t font object remains alive.
+ *
+ * Use this version unless you know you have good reasons not to.
+ *
+ * Return value: (transfer full): the new #hb_font_t font object
  *
- * Return value: (transfer full):
  * Since: 0.9.38
  **/
 hb_font_t *
@@ -793,6 +879,19 @@ _release_blob (FT_Face ft_face)
   hb_blob_destroy ((hb_blob_t *) ft_face->generic.data);
 }
 
+/**
+ * hb_ft_font_set_funcs:
+ * @font: #hb_font_t to work upon
+ *
+ * Configures the font-functions structure of the specified
+ * #hb_font_t font object to use FreeType font functions.
+ *
+ * <note>Note: Internally, this function creates an FT_Face.
+ * You should use this FT_Face when you create an #hb_face_t
+ * with hb_ft_face_create().</note>
+ *
+ * Since: 1.0.5
+ **/
 void
 hb_ft_font_set_funcs (hb_font_t *font)
 {